1. Field of the Invention
The present invention relates to an image forming apparatus for use in a copying machine, a facsimile, a laser beam printer, or the like, adapted to form an image by visualizing an electrostatic latent image with a two-component developer containing a mixture of toner and carrier.
2. Discussion of Prior Art
In a known image forming apparatus using electrophotography, an electrostatic latent image is formed on a surface of a photoconductor having a photoconductive layer serving as an image bearing member by exposing the surface of the photoreceptor which has been uniformly charged. Subsequently, the electrostatic latent image on the photoreconductor is developed with toner to form a toner image. The toner image is then transferred to a recording member such as a transfer sheet. The transferred toner image is finally fixed on the recording member by application of heat and pressure.
As the developer, a single component developer composed only of a toner and a two-component developer composed of a toner and a carrier are known. The two-component developer is currently major.
Great endeavor has been made to obtain high grade images with the image forming apparatus. In particular, reproducibility of fine line images and uniformity in density of 100% solid image areas are very important factors. To improve uniformity of the density of solid images, it is effective to use a toner having a small particle diameter and to minimize the maldistribution of charges at peripheries of a latent image for a solid image. The reproducibility of fine line images may be improved by using a toner having particle sizes distributed in a small diameter side, because fine particles are apt to be concentrated in an area, such as a fine line area, in which charges are concentrated.
One problem with the conventional image forming devices using fine toner particles is fouling of a surface of a developer bearing member such as a developing sleeve. When such fouling proceeds, there is formed deposits of the toner adhering on the sleeve surface by fusion. This is usually referred to as filming. Once filming occurs, cleaning of the developing sleeve with jet air is no longer effective and a solvent must be used to clean it.